Jet pump refrigeration system



y 20, 1954 E. P. NEUMANN ET AL 2,683,971

TO EVAPORATOR JET PUMP REFRIGERATION SYSTEM Filed Oct. 21, 1952 FR OM EVAPORATOR 22 [O0 JNVENTORS ERNEST P. NEUMANN BY FERDINAND LUSTWERK ATTORNEYS Patented July 20, 1954 UNITED STATES PAENT OFFICE JET PUMP REFRIGERATION SYSTEM Ernest P. Neumann and Ferdinand Lustwerk,

Lincoln, Mass., assignors to Ultrasonic Corporation, Cambridge, Mass, a corporation of Massachusetts Application October 21, 1952, Serial No. 315,888

6 Claims. (Cl. 62-41755) it having cooling fins l8 secured thereto. Refrigerant gas from the evaporator is pumped and compressed by the jet pumps working in tandem, the eliluent therefrom being thereafter passed through a condenser 22 in which it yields heat liquefies.

From the condenser 22 the liquid refrigerant, together with the motive fluid injected from the boiler l2, passes through a tube 24 and into a The primary object of the present invention is gravity separating chamber 26. As shown the to eliminate malfunctions of an injector-fed connections are established for operation with a boiler employed to provide pressurized vapor of heavier refrigerant and a lighter motive fluid. the motive fluid. Hence the former collects at the bottom of the Another object of the invention is to render separator 23 and is drawn off through a pipe 2% the boiler operation less directly responsive to the and returned to the evaporator through a con dimensions of the injector employed to feed it, ventional expansion valve (not shown). thus facilitating the design of the system and re- The lighter motive fluid fills the upper portion ducing the cost of constructing the injector. of the separator and is drawn oil? through an An important feature of the invention resides injector contained in a housing 36 and thereby in the combination of a boiler fed by an injector 2o pumped back to the boiler i2. The injector in and feeding an ejector coupled to drive refrigthe housing 36 is powered by vapor exhausted erant under compression into a condenser and from the boiler l2 and conducted to the injector a capillary tube connected between the boiler and through an external tube 13. Heat for the boiler the condenser, the capillary serving to drain the is supplied by electricity through a resistance boiler above a predetermined level and prevent g5 element in the form of nichrome windings served stoppage due to excessive feeding. by a supply line 32.

The dimensions of the boiler in a system de- In operation the liquid refrigerant passes from signed for ordinary household use are relatively the separator 26 into the evaporator Where it is small, a fact which would in return require a very expanded and heated. From the evaporator the small injector, so small as to introduce grave dif- 3O gaseous refrigerant is drawn by the upper jet ficulties in forming and assembling its parts. pump in the housing M into the tube [5 where However, by providing a capillary drain from it is given preliminary compression and wherein the boiler, it becomes possible to employ an overpart of its heat is extracted and radiated to the size injector without flooding the boiler. A capilatmosphere by the cooling fins E8. The partially lary will accept a satisfactorily large flow of liquid compressed refrigerant then passes through the but only a negligible flow of gas. Hence the tube ltinto the second jet pump into the housing presence of the capillary does not result in any it where it is further compressed and then disserious drop in boiler pressure. charged into the condenser 22 where additional These and other objects and features of the heat is given up and wherein the gaseous refriginvention will be more readily understood and erant condenses to the liquid state and then appreciated from the following detailed descrippasses into the tubular separating chamber 23 tion of a preferred embodiment thereof selected where it settles to the bottom readily to pass: for purposes of illustration and shown in the again through the refrigerating cycle. On the ac ompanyin draw in w h the ur is a other hand, the motive fluid is withdrawn from di r mm t V w p ly in r ti the top of the separating chamber 26 by the jet through t r, injector, and jet p mp assempump in the housing 30, by means of which the yliquid is injected into the boiler I2 and therein In advance of a discussion of the details Of the heated until it vaporizes and leaves the top of the embodiments herein shown be helpful first bailey under pressure to erve as the motive to consider the general organization of the sysfor th t stage jet pump, Also a, portion of tern. There is provided a conventional evaporathe vapor from the boiler passes through the tor of standard Co structio (n 1? S wn) a tube '58 and serves as the motive fluid to operate a boiler E2 of elongated tubular form. The boiler the injector '12 in the pump 30 and thus to feed 52 serves a pair of jet pumps contained in housthe boiler I2. ings hi and I4 and connected in series by a pipe 55 With the foregoing general remarks in mind the details of the boiler and jet pump assembly can more easily be understood. As shown the boiler comprises an outer tube or shell i2 within which and concentrically arranged is a tube around which is wrapped a spiral of nichrome wire 39, the latter being protected in turn by a casing 4|. There is thus formed an elongated annular chamber 42 lying between the casing 4| and the shell l2. At the bottom of the tube 40 there is disposed a ball check valve 44 serving to prevent the draining of liquid from the bottom of the boiler. At the top of the tube 40 there is a second ball check valve working against a spring 52 set in a socket formed in a plug 48 serving to close the top of the shell l2. Adjacent the upper end of the boiler shell i2 is an outlet 54 which is coupled to an injector nozzle 56 having its inner passage so shaped that vapor leaving the boiler shell l2 first encounters a converging wall portion in which the pressure or" the vapor is raised and then a diverging or diffuser portion which discharges into the housing l4. Refrigerant gas is admitted into the housing M through a pipe 58 connected into the exhaust end of the evaporator. One end of the tube I6 is enlarged as shown at 66 and projected within the housing 14 opposite the injector nozzle 56.

The rush of vapor through the nozzle 56 and into the tube 69 carries with it refrigerant gas entering the housing l4 through the pipe 58 and the refrigerant gas thus entrained is com-- pressed to a preliminary extent in the tube another result, of course, is to create suction in the line 53 leading from the evaporator. Disposed below the outlet 54 is a second outlet 62 receiving one end of a bellows connection as which is coupled at its outer end to the housing I 4' and to a second and smaller jet nozzle 66. The condenser tube 22 has an enlarged head projected into the housing i opposite the diffuser end of the nozzle 56, the result being that partially compressed refrigerant together with motive fluid introduced into the tube I5 is discharged into the housing l4 and then entrained in the rush of vapor through the nozzle 65 and dispatched through the condenser tube 22 where the refrigerant will condense to a liquid as it passes through the condenser 22. As a matter of fact, most of the motive fluid will be condensed by the time it reaches the bottom of the housing 114, and we provide a trapped drain 68 leading from the bottom of the housing hi to the top of the separator 26, the drain 68 having a U-shaped loop portion effective to provide a head of pressure sufficient to prevent liquid in the separator from blowing back into the housing I4 through the drain 68.

Adjacent the upper end of the separator there is provided an outlet pipe 70 leading to a housing 38 in which is contained a jet nozzle '12 disposed opposite an injector nozzle 'i-l leading to a vertical pipe 5 which is connected into the bottom of the tube 40 below the ball check valve 44. Adjacent the bottom of the boiler shell 42 there is provided an annular housing enclosing a conduit 16 leading to a tube '78 which in turn terminates in the nozzle 12.

For a discussion of the operation of the elements thus far described, the reader is referred v to our copending application identified above. Coming now to the improvement with which the present application is concerned, it will be evident that a thin capillary tube Hill has a horizontal leg connected to the interior boiler tube 40 at a point about three quarters of the distance from the lower check valve 44 to the upper check valve 50, or wherever it is desired to establish the maximum height of the level of liquid in the boiler. The other end of the capillary tube I comprises a vertical leg connected to the condenser tube 22 at a point substantially below the first connection.

In operating the system the injection system I2, 14 may be dimensioned to feed a small excess of liquid to the boiler, that is to say an amount exceeding that which is normally vaporized in the boiler. When the liquid level rises to the end of the tube H10, it begins to drain through the tube [60, an effect which is assisted by the pressure Within the boiler and by the suction of the liquid column formed in the vertical leg of the tube I08. However, when the level of the liquid in the boiler drops below the end of the tube I00, the flow of gas through the tube is negligible, since the mass flow through a capillary is much less for a gas than for a liquid. Although a capillary tube is quite satisfactory, a larger tube with a constriction or restricted orifice may be substituted therefor with no loss of efficiency. The actual. diameter of the tube will depend upon the size of the boiler and other elements of the system, and those skilled in the art will readily understand what dimensions will be applicable.

The advantages resulting from the emplojment of the improvements herein disclosed include not only the elimination of malfunction due to flooding of the boiler but also the feasibility of injector nozzles of larger dimensions and cheaper cost, since very difficult machining problems are encountered in the fabrication of very small nozzles.

Having now disclosed and illustrated a preferred embodiment of the invention, what we claim as new and desire to secure by Letters Patent of the United States is:

1. In a refrigeration system including a boiler, a condenser, a jet pump connected to said boiler and to said condenser, the combination of an injector driven by a portion of the exhaust from said boiler and connected to the inlet of said boiler and said condenser for entraining liquid from said condenser into said boiler, and a relatively small tube connecting said boiler at a predetermined height therein to said condenser.

2. In a refrigeration system including a boiler, a condenser, a jet pump connected to said boiler and to said condenser, the combination of an injector driven by a portion of the exhaust from said boiler and connected to the inlet of said boiler and said condenser for entraining liquid from said condenser into said boiler, and a cal lllary tube connecting said boiler at a predetermined height therein to said condenser.

Apparatus of the class described, comprising a boiler, a condenser, a jet pump connecting the exhaust of the boiler to the condenser, an injector receiving vapor from said boiler and connected to pump liquid from the condenser to the boiler, and a tube having a horizontal leg connected to the boiler a predetermined distance above its base and a vertical leg depending from the level of the horizontal leg and connected to the condenser for passing directly to said condenser liquid in said boiler above the level of the horizontal leg of said tube.

4. Apparatus of the class described, comprising a boiler, a condenser, a jet pump connecting the exhaust of the boiler to the condenser, an

injector receiving vapor from said boiler and connected to pump liquid from the condenser to the boiler, and a capillary tube having a horizontal leg connected to the boiler a predetermined distance above its base and a vertical leg depending from the level of the horizontal leg and connected to the condenser for passing directly to said condenser liquid in said boiler above the level of the horizontal leg of said tube.

5. Apparatus of the class described, comprising a boiler having an inlet for liquid and an exhaust passage for vapor, pressure responsive check valves controlling the inlet and the exhaust passage, a pair of jet pumps connected in parallel to said exhaust passage, a condenser connected to said jet pumps, a tank connected to said condenser, a capillary tube connected between an intermediate point of the boiler and said condenser, an injector connected to said exhaust passage and to said tank, and Walls forming a chamber connected at one end to said 6 boiler inlet and at the other end to said injector.

6. Apparatus of the class described, comprising a boiler having an inlet for liquid and an exhaust passage for vapor, pressure responsive check valves controlling the inlet and the exhaust passage, a, pair of jet pumps connected in parallel to said exhaust passage, a condenser connected to said jet pumps, a capillary connected between said condenser and said boiler, a tank connected to said condenser, an injector connected to said exhaust passage and to said tank, and walls forming a chamber interconnecting said injector and said boiler inlet.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Re.21,894 Randel Sept. 2, 1941 2,001,697 Altenkirck May 21, 1935 2,301,839 Work et a1 NOV. 10, 1942 

